Lock mechanisms which utilize reciprocating combinating tumblers are well known in the art. Such lock mechanisms are commonly used, for example, to prevent unauthorized access to a place (e.g., a house, an apartment, an office, a desk, etc.) and to prevent the removal of objects therefrom. Such lock mechanisms are also used to secure transportable goods (e.g., skis, luggage, bicycles, surfboards, canoes, etc.) to a vehicle. In most instances, a transporter system (commonly known as a "load carrier") is mounted to the roof of the vehicle and the transportable goods are locked thereto. Examples of load carriers include ski racks, luggage racks, and boat carriers.
Most load carriers include a framework which is assembled from discrete component parts. In order to provide sufficient strength and durability to the framework as a whole, each component part is typically fabricated from either metal or high impact plastic material (e.g., polycarbonate plastic). A key-operated lock mechanism is also provided for locking the transportable goods to the framework. The lock mechanism usually comprises a conventional lock plug assembly having a plurality of flat reciprocating metal tumblers disposed therein. In most instances, the lock plug assembly is received by an aperture formed in one or more of the high impact plastic component parts of the framework. Of course, in order to prevent rotation of the lock plug assembly when its in its locked position (i.e., when the tumblers are extended), the aperture must include at least one longitudinal spline.
One notable disadvantage of such lock mechanisms is that the metal tumblers can be used to cut through the high impact plastic material of the framework, especially when the load carrier is subjected to cold temperatures. For example, when a tool or utensil is inserted into the lock plug assembly and a sufficient rotational force is applied thereto, the flat metal tumblers will cut, shear, or break through the plastic material which surrounds the aperture (i.e., the plastic material immediately adjacent to the spline). In this way, vandals or thieves may defeat the lock mechanism and gain access to the goods being transported by the vehicle. Of course, when the lock mechanism is defeated in this way, the framework of the load carrier is also damaged.
An additional deficiency of such lock plug assemblies is that they are very difficult, if not impossible, to remove from the framework of the load carrier during replacement, repair and/or servicing because the rear portion of such lock plug assemblies is generally inaccessibly positioned within the aperture. A further inconvenience associated with such lock plug assemblies is that snow, ice, dust, and other debris can enter the keyway slot which may damage the tumblers and/or cause the lock mechanism to freeze-up or become inoperable.